Republicans are working on emergency plans to salvage their convention as tropical storm Isaac hurtles towards New Orleans, with party officials acknowledging that their carefully-choreographed event could face further disruption.

The Republicans, still haunted by the fatal delays of President Bush in the aftermath of hurricane Katrina exactly seven years ago, would find it difficult to push ahead with their convention in Tampa in the event of serious flooding.

Organisers said for the first time that the remaining days – Tuesday, Wednesday and Thursday – may also be disrupted by Isaac hitting the Gulf coast. They expressed hope that the convention, with a reshaped schedule, would go ahead, but conceded that in a worst-case scenario the whole thing might have to be cancelled.

Under that scenario, Romney would express regret over events in New Orleans and say that human life takes precedence over politics.

Senior Republicans, including Louisiana governor Bobby Jindal and Florida governor Rick Scott, have pulled out of the convention to focus on leading the Isaac response in their states.

Isaac has already affected the Republican convention, an event intended as a launchpad for Mitt Romney's bid for the White House and an occasion normally attracting guaranteed primetime television spots.

It should have kicked off on Monday, but the Republican national committee cancelled the first day amid severe weather warnings for Florida. However, as delegates gathered for the convention's formal opening followed by its immediate adjournment, the National Hurricane Center lifted the tropical storm warning for Tampa.

Romney, who remains in New Hampshire rehearsing his conference speech, expressed surprised when asked about the convention being cancelled. "Got a great convention ahead," he told the Washington Post.

The Republicans intended to use the event to criticise Barack Obama's economic record and build up Romney's profile. But television networks are now sending teams to New Orleans, and focus on the imminent storm will almost certainly deflect attention from the convention.

RNC chairman Reince Priebus admitted that the convention would have to compete with the weather story. "It's a terrible thing. We certainly hope it doesn't develop into something stronger. We have to tell the Mitt Romney story and prosecute the president on what he promised, what he delivered. And at the same time you have to report on this storm, because it is something that people need to know about," he told NBC.

The convention was officially opened on Monday but went into recess again after less than 10 minutes, and was postponed until Tuesday. Priebus, speaking at the podium in front of mainly journalists, expressed hope that those in the path of Isaac will be kept out off harm's way.

Priebus also launched a political gimmick, a clock ticking for the duration of the convention that will total the amount of federal debt accumulated during that time. There was also a prayer and a short video of Romney expressing his love of America.

Isaac could also give Barack Obama an opportunity to make a high-profile intervention. Having learned the lessons from Bush, Obama would almost certainly head directly for New Orleans in the event of serious damage.

Obama called the governors of the states in the path of the storm to offer government assistance.

The compressed convention schedule caused another high-profile cancellation: entrepreneur and Romney backer Donald Trump was due to have a speaking slot on Monday, but was bumped from the schedule.

The conservative talk show host Mike Huckabee has also pulled out. The former Arkansas governor had been due to speak Monday and has not been rescheduled for later in the week.

Huckabee's non-appearance, though, could prove a blessing for the convention organisers, because he has been one of the few high-profile Republicans to speak out on behalf of the party's senatorial candidate Todd Akin, who is at the centre of the rape/abortion row. If Huckabee had spoken, it would have renewed a controversy the party has been trying to shove to the sidelines.

The seventh anniversary of Katrina will fall on Wednesday. New Orleans has a special resonance for Republicans because of Bush and because of ideological arguments about the level of federal intervention, and this would make it difficult for the party to continue with a raucous convention gathering.

Rich Galen, a Republican strategist, said the tone of the conference might have to be changed. "You can tone down the happy-days-are-here-again a bit," he told AP.

Russ Schriefer, who is organising the convention schedule, told a press conference on Monday the party is not yet seriously looking at extending into Friday. "We are planning on Tuesday, Wednesday and Thursday. If the weather changes in a way that we have to make some changes … it's a hypothetical question, so I don't want to answer it in that way."

Schriefer said that the schedule was being reorganised to accommodate speakers who had been dropped. Speakers had been asked to shorten their speeches.

"There's a weather event. We all know that," Schriefer said, responding to a question about the impact of the storm heading towards New Orleans.

Various parties and events on the sidelines of the convention were cancelled on Monday, though Tampa was experiencing little more than heavy rain.

A protest organised for Monday was among the events to suffer. Only a few hundred protesters turned up out of a predicted 5,000, and the organisers blamed the warnings about Isaac.

The focus on the storm had one positive for the Republicans, distracting attention from a report that New Jersey governor Chris Christie had turned down the vice-presidential slot because he thought Obama was likely to win the election.

Christie is lined up to be the keynote speaker, with the primetime television slot, on Tuesday night. According to the New York Post, Christie refused to give up his governorship to be Romney's running mate.

Christie, though a popular figure, would have annoyed the conservative wing of the party because he is less hardline than many Republicans over guns and abortion.

Romney campaign officials denied the story.

Romney may have considered Christie early on when his strategy was to win over independent swing voters but when he shifted to a new strategy of cementing the party base then his eventual choice, Paul Ryan, is a better fit.